I'm not sure if this is exactly what you want, I may have mis-understood, but here is my stab at it:

use warnings;
use strict;

local $/ = "";   # Paragraph mode

# Capture the header from the top of the file
# not sure what you want doing with this though!
my $header = <DATA>;
chomp $header;
print "Header: <$header>\n\n";

# Now process the other records
while (<DATA>) {
    chomp;
    my @lines = split("\n");
    
    # extract header
    my $head = shift @lines;
    
    # Append header as an end column
    for (@lines) { $_ .= $head }

    # Display result
    local $, = "\n";
    print @lines,"\n";
}

__DATA__
FUNCTION VCC= 4.50V, VIL=0V, VIH=3V, VOL=VOH=1.5V    PASS    
4    730     0     
FUNCTION VCC= 5.50V, VIL=0V, VIH=3V, VOL=VOH=1.5V    PASS    

VOL TEST @VCC= 4.5V, VIL=2V, VIH=5.5V
5    796    6   421.5 mV,RNG1   60.00 mA,M100                         
+  
5    801        381.5 m                             0      500.0 m    
+  
5    815    8   417.0 mV,RNG1   60.00 mA,M100                         
+  
5    820        377.0 m                             0      500.0 m    
+  

VOH1 TEST @VCC=4.5V, VIL=0.8V, VIH=5.5V
6    886    6   2.920  V,RNG2  -3.015 mA,M100   2.500  V   4.500  V   
+  
6    899    6   2.920  V,RNG2  -3.015 mA,M100   2.500  V   4.500  V   
+  
6    912    6   2.916  V,RNG2  -3.015 mA,M100   2.500  V   4.500  V   
+  
6    925    6   2.916  V,RNG2  -3.015 mA,M100   2.500  V   4.500  V   
+  
6    938    8   2.920  V,RNG2  -3.015 mA,M100   2.500  V   4.500  V
[download]

Gives: (note that lines are wrapped around +)

Header: <FUNCTION VCC= 4.50V, VIL=0V, VIH=3V, VOL=VOH=1.5V    PASS
4    730            0
FUNCTION VCC= 5.50V, VIL=0V, VIH=3V, VOL=VOH=1.5V    PASS    >

5    796    6   421.5 mV,RNG1   60.00 mA,M100                         
+  VOL TEST @VCC= 4.5V, VIL=2V, VIH=5.5V
5    801        381.5 m                             0      500.0 m    
+  VOL TEST @VCC= 4.5V, VIL=2V, VIH=5.5V
5    815    8   417.0 mV,RNG1   60.00 mA,M100                         
+  VOL TEST @VCC= 4.5V, VIL=2V, VIH=5.5V
5    820        377.0 m                             0      500.0 m    
+  VOL TEST @VCC= 4.5V, VIL=2V, VIH=5.5V

6    886    6   2.920  V,RNG2  -3.015 mA,M100   2.500  V   4.500  V   
+  VOH1 TEST @VCC=4.5V, VIL=0.8V, VIH=5.5V
6    899    6   2.920  V,RNG2  -3.015 mA,M100   2.500  V   4.500  V   
+  VOH1 TEST @VCC=4.5V, VIL=0.8V, VIH=5.5V
6    912    6   2.916  V,RNG2  -3.015 mA,M100   2.500  V   4.500  V   
+  VOH1 TEST @VCC=4.5V, VIL=0.8V, VIH=5.5V
6    925    6   2.916  V,RNG2  -3.015 mA,M100   2.500  V   4.500  V   
+  VOH1 TEST @VCC=4.5V, VIL=0.8V, VIH=5.5V
6    938    8   2.920  V,RNG2  -3.015 mA,M100   2.500  V   4.500  V   
+  VOH1 TEST @VCC=4.5V, VIL=0.8V, VIH=5.5V
[download]